Exploring Species Assemblages in Kruger National Park, South Africa

Abstract

We examined hypotheses of spatial association arising from exclusion or indirect competitive interactions, using 13 years of gridded mammal census data from Kruger National Park, South Africa. As interactions occur at different scales, we explored the data at 1, 5, 10, and 15 km2. We proposed four hypotheses structuring the mammal community: H1, predator exclusion of herbivores by carnivores (apparent direct competition); H2-H4: indirect competition produced by each of three types of herbivore diet specialization: H2, ruminants and non-ruminants; H3, grazers and browsers, and H4, a four-way division of small and large grazers and browsers. We used the software CoOccur to implement a robust test for evidence of our hypotheses against null models of community assemblage. At 5, 10, and 15 km2scales, the results supported a competition/exclusion mechanism in the majority of years for hypotheses H1, H3, and H4, and facilitation in H2. At the finest spatial scale (1 km2), we saw patterns resembling a mixture of competitive, neutral and facilitative process. These results suggest strong, large-scale effects of interspecific interactions on distributions of African megafauna, which may not operate at a more local (1 km2) scale, underscoring the importance of scale and mechanism in the guild structure of communities.